3GPP LTE and LTE-Advanced (LTE-A) are one of the next generation cellular communication standards, which create a new series of specifications for the new evolving radio-access technology. With respect to multiplexing solutions, LTE and LTE-Advanced provide two modes, Frequency Division Duplex (FDD) and Time Division Duplex (TDD).
In LTE release 8, Transmission Time Interval (TTI) bundling has been introduced to improve the cell coverage. Coverage benefit has been observed from TTI bundling enhancements for uplink (UL) VoIP and medium size traffic. TTI bundling is generally supported by the FDD system and the TDD system with UL/DL configurations 0, 1 and 6.
So far, a subframe configuration comprising 5 downlink (DL) subframes and 2UL subframes, as well as special subframes, is used in TD-SCDMA network (R1-121712, CMCC) in F band (1880-1920 MHz) and A band (2010-2025 MHz). For a scenario between a TDD system and the TD-SCDMA network, wherein the TDD system is deployed in either F band, A band or E band (2300-2400 MHz), a co-existence problem shall be taken into account.
Since the TD-SCDMA network usually uses a configuration of 5DL/2UL subframes, the most suitable UL/DL configuration for LTE TDD system or TD-LTE or TD-LTE-Advanced is configuration 2. However, for configuration 2, it can't use TTI bundling to improve the cell coverage.
In view of the foregoing problem, there is a need to find a solution for performing TTI bundling with configuration 2 and/or more UL/DL configurations, so as to enhance coverage in the TDD system.